Wheel speed sensors for automobiles typically utilize an indexing disc mounted on a wheel and a pickup that detects the passage of marker elements carried by the disc as the wheel turns. This pickup can be mechanical, optical or magnetic.
A typical existing arrangement uses a multi-toothed, steel disc mounted on a wheel along with a pickup that detects the presence of magnetic material on a tooth, or its absence when over a gap. A Hall Field Effect proximity sensor is employed as the pickup. This is a device of choice because of its high reliability and ease of use.
In this typical existing system, measurements are made by counting multiple teeth for a fixed sampling interval. For accuracy the disc is relatively large and carries many teeth. Nevertheless, precision is limited by the number of teeth present on the disc.
Both the disc and pickup elements are carried by the wheel and axle support structure and are therefore separated from the vehicle chassis by the wheel suspension system. This creates the difficulties of providing flexible connectors to the wheel assembly carrying the sensor and exposes the sensor to road shocks.
In a front wheel drive vehicle mechanical power is transferred to the wheels through a transaxle. This occurs through shafts that include constant velocity--"CV--" joints. This type of power train provides an opportunity to simplify the arrangement by which front wheel speed on a front wheel drive car can be measured.
The invention in its general form will first be described, and then its implementation in terms of specific embodiments will be detailed with reference to the drawings following hereafter. These embodiments are intended to demonstrate the principle of the invention, and the manner of its implementation. The invention in its broadest and more specific forms will then be further described, and defined, in each of the individual claims which conclude this Specification.